Tasteless, colorless, odorless, carbon monoxide (CO) is produced to varying degrees by almost every fuel burning appliance and other combustion equipment, including fireplaces, grills and space heaters. When the equipment is working right, very little CO gas escapes, and what does gets vented harmlessly to the outside. When something goes wrong with the equipment or the venting, CO becomes one of America's most deadly household hazards.

Here's a little quiz to find out how much you know about the gas that has come to be known as the "Silent Killer." Answers are at the end of the article.

1. How many people in the U.S. die each year from CO poisoning?

A. Dozens

B. Hundreds

C. Thousands

D. Unknown

2. Which of the following do NOT produce carbon monoxide?

A. Gas water heater

B. Gas furnace

C. Electric wall heater

D. Automobile

3. Which of the following are symptoms of CO poisoning?

A. Headache, dizziness

B. Nausea, weakness

C. Sleepiness, disorientation

D. None of the above

E. All of the above

4. How many parts per million is considered a safe level of CO concentration?

A. 10 ppm

B. 0

C. 100 ppm

D. 50 ppm

5. What should you do if you experience any of the CO symptoms?

A. Vacate the house and call your local emergency number.

B. Try to find the source of the problem and fix it.

C. Open doors and windows.

D. Take two aspirin and call your doctor.

6. Which of the following might indicate a CO problem?

A. Improper connections on vents and chimneys.

B. Visible rust or stains on vents and chimneys.

C. An appliance that makes unusual sounds or emits an unusual smell.

D. An appliance that keeps shutting off.

E. All of the above.

7. Which is the most dangerous season for carbon monoxide poisoning?

A. Winter

B. Spring

C. Summer

D. Fall

8. Which of the following does NOT help prevent CO poisoning?

A. Installation and regular maintenance by a qualified service technician on all combustion appliances, such as furnaces, water heaters, gas dryers, etc.
B. Regular inspection of chimneys and flues for blockages, corrosion and loose connections.
C. Tightly sealed doors and windows.
D. Installation of CO alarms throughout the home.

9. Where is the best place to install a CO detector?

A. In the basement or utility room near combustion appliances.

B. Outside a bedroom.

C. In the kitchen.

D. In the family room.

10. All heating contractors know how to detect excessive CO and take remedial action.

A. True

B. False

ANSWERS:

1. D. Technically, you would be correct if you answered either B or C as well. Statistics about CO poisonings are hard to come by, because the condition is frequently misdiagnosed as flu or other ailments.

The Consumer Product Safety Commission says that "nearly 300 people" die each year from this toxic substance. The American Medical Association estimates about 1,500 fatalities a year. According to the AMA, about another 10,000 people a year take ill from carbon monoxide.

3. E. Headache, dizziness, nausea, weakness, sleepiness and disorientation are all symptoms of CO poisoning, though a victim may not experience every one. Unfortunately, these same symptoms are associated with flu, food poisoning and other afflictions, leading to many misdiagnoses.

A cherry red face is a possible sign of CO poisoning. One technique doctors use to diagnose the problem is a simple test of adding a sodium hydroxide solution to dilute blood and look for a change in color.

At high levels of CO concentration, victims may lose consciousness. At this point permanent brain damage or death is a real danger.

If you or someone else in your household experiences any or all of the CO symptoms, spend some time outside and see if you feel better. If the outdoor exposure speeds your recovery, it can be taken as a possible indicator of a CO problem inside the home.

4. A. Zero carbon monoxide may be an unattainable goal in our modern homes with so many combustion appliances. OSHA and EPA define a safe level of exposure as between 9 and 50 ppm for no more than eight hours, no more than once a year. Infants and people with heart conditions are more susceptible to CO poisoning than healthy adults.

5. A. Opening doors and windows can be an effective emergency response. However, some emergency authorities advise against this because it makes it hard for them to determine whether there is a CO problem when they enter the house to inspect. Vacating the premises is always a good idea.

6. E. Broken or blocked vents and flues are probably the most common cause of CO buildup. If you see any holes or disconnections, or rust stains indicating corrosion, get the problem fixed immediately. Also be sure to put a guard on top of rooftop vents to prevent birds' nests or other debris from falling into the chimney.

Carbon monoxide results from incomplete combustion. An appliance that makes unusual noises should be inspected by a professional. Many new appliances have safety components attached that prevent operation if an unsafe condition exists. So if an appliance keeps shutting off, call a service person instead of continuing to turn it back on.

7. A. Carbon monoxide danger is greatest in winter when heating equipment gets its most strenuous workout, and when doors and windows are shut tight.

8. C. Modern homes are better insulated than ever because of energy efficiency concerns. However, draft-free homes are also more susceptible to CO leaks. The best preventive measure is to deal only with heating professionals you trust for installations and regular checkups.

9. B. The greatest danger from CO occurs when people are asleep and unable to detect any of the symptoms. You want an alarm to sound where people will hear it. Installing a detector near the CO-emitting equipment will likely result in many false alarms.

10. B. Unfortunately, even many heating professionals lack the training and/or equipment needed to diagnose excessive CO and take remedial action. In a 1995 survey of 104 contractors in Iowa, 25 didn't have the equipment to measure CO and 61 lacked appropriate training.

Don't trust the recommendation of any contractor who doesn't have a calibrated instrument capable of measuring CO in room air and in the combustion products. CO is undetectable without such gear. Also ask what kind of training the service personnel have received in measuring and investigating carbon monoxide cases.